Polycyclic aromatic sulfur heterocycles (PASHs) are sulfur analogues of polycyclic aromatic hydrocarbons (PAHs) commonly found in environmental samples exposed to oil contamination. The determination of PASHs in complex samples is far more difficult than PAHs because of the sulfur atom in the heterocyclic ring, which increases the total number of possible isomeric compounds. Since their toxicological properties vary considerably from isomer to isomer, the unambiguous determination of specific isomers in environmental samples is crucial for ecotoxicological purposes and human safety. GC-MS has been the primary analytical technique for the determination of PASHs in environmental samples. Unfortunately, as the number of aromatic rings increases, the increasing number of possible isomers with similar retention times and nearly identical mass fragmentation patterns makes separation and identification difficult. Recent developments in our group have shown that the analysis of PASHs in complex environmental extracts is best accomplished with sample fractionation via normal phase liquid chromatography (NPLC) and subsequent analysis of NPLC fractions via GC-MS. Specific PASHs are then identified on the bases of NPLC retention times, GC retention times and mass spectra. The first part of this dissertation investigates the analytical potential of low-temperature photoluminescence spectroscopy for the analysis of phenanthrothiophenes with molecular mass – 234 Da in NPLC fractions. Excitation and emission spectra recorded from n-alkane solutions at 77K and 4.2K showed strong phosphorescence from all the studied isomers at cryogenic temperatures. The analytical figures of merit obtained under steady state (fluorescence) and time-resolved (phosphorescence) conditions provided limits of detection at the parts-per-billion (ng mL-1) concentration levels. Processing 77K and 4.2K phosphorescence data with parallel factor analysis showed to be a robust approach that requires no further separation of NPLC fractions. The second part of this dissertation studies the adsorption of PASHs on microplastics (MPs); i.e., plastic particulates with dimensions ranging from 0.1 to 5000 µm. Once released into aquatic environments, PASHs have the potential to bioaccumulate and cause toxic effects in aquatic organisms. Since MPs can be accidently ingested by biota, the adsorption of PASHs on the surface of MPs might be a credible route by which PASHs enter the marine food web. To the extent of our literature search, there are no reports on the interaction of PASHs with MPs.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Arif, Sadia, "Photoluminescence Properties of Polycyclic Aromatic Sulfur Heterocycles and Their Sorption and Desorption onto Microplastics." (2021). Electronic Theses and Dissertations, 2020-. 468.